The advent of two-way messaging systems has enabled new communication applications. One such application is the ability to conduct polling exercises. For example, an outbound message can be transmitted by a fixed portion of a two-way messaging system using a group address to which a plurality of portable subscriber units are responsive. The outbound message can ask a question and provide some candidate responses, e.g., "yes" and "no". Users of the subscriber units polled can then each select a response to be returned on an inbound channel. Unfortunately, however, when many users are polled, inbound channel traffic can temporarily exceed the traffic capacity of the inbound channel, blocking other inbound traffic and generally snarling two-way communications.
Similarly, when large groups of subscriber units are sent an information services (IS) message on a common group address, too many acknowledgments of the message can also snarl communications. For this reason, portable subscriber units typically have been programmed to send only negative acknowledgments to IS messages. (If no response to an IS message is received by the fixed portion, a positive acknowledgment is assumed.) The negative acknowledgments allow service providers to assess the reliability of IS message transmissions. Still, if the IS message is sent to a large enough group of subscriber units, the quantity of negative acknowledgments can again create excessive inbound traffic.
Thus, what is needed is method and apparatus for reducing inbound transmissions in a two-way messaging system, particularly in response to messages sent to a group address. The method and apparatus preferably will allow polling exercises to continue with minor impact, and further will allow service providers to assess the reliability of IS message transmissions.